PGFplots error bars.

\documentclass{article}
\usepackage{pgfplots}
%
\begin{document}
\thispagestyle{empty}
\begin{tikzpicture}
\begin{axis}
\addplot plot[error bars/.cd,
y dir=both, y explicit,
x dir=both, x explicit]
coordinates {
(0,0) +- (0.5, 0.1)
(1,1) +- (0.2, 0.3)
};
\end{axis}
\end{tikzpicture}

\end{document}